Eared seals differ from the true seals in having small external earflaps and hind flippers that can be turned to face forwards. Together with strong front flippers, this gives them extra mobility on land and an adult fur seal can move extremely fast across the beach if it has to. They also use their front flippers for swimming, whereas true seals use their hind flippers.

Like other Eared seals, the male Juan Fernandez fur sealis considerably larger than the female.

Like other fur seals, the Juan Fernandez fur seal was long hunted for its skin and oil. Remarkably, the Juan Fernandez fur seal was considered extinct until it was happily rediscovered in 1965, although it nevertheless remains rare.

Like most fur seals, this species has an elongated, slender body and a long, pointed snout and flippers. Adult males have a particularly long muzzle that may be slightly down-curved at the tip, and which ends in a large, bulbous, fleshy nose, creating a shark-like silhouette. Adult males also develop thicker and more muscular necks, surrounded by a mane of long, coarse, dark hair with silver tips, giving the mane a frosted appearance. The necks and fore-flippers of the males are usually scarred from fighting. The back and belly are dark, blackish-brown in males, while the crown down to the ears and nape to the shoulders sometimes appear silvery-grey, against a darker throat and neck. Adult females are grey-brown to dark brown above, and variably paler below, especially on the chest and underside of the neck, which can be creamy grey, and there may be areas of lighter colour on the face. Both sexes have whitish-cream whiskers.

The body is similar to that of most fur seals, slender and elongated, with males ranging from 150 to 200 cm, and females at about 140 cm in length. Weight of males is about 140 kg, and females weigh about 50 kg. All species of Arctocephalus have similar coloration. The under fur and bases of flippers are described as rich and chestnut brown in color. Males have a thick mane of long hair that is dark with white tips, giving the mane a frosted appearance. Males have a long pointed nose which is distinctive. Females have a noticeable grey-brown to dark brown coloration on the back but are paler below, especially on the chest and underside of the neck.